This application pertains to the art of control systems for electrically controlled or operated devices including motor vehicles. The invention finds particular application in anti-theft systems for cars, trucks, and other motor vehicles and will be described with particular reference thereto. It is to be appreciated, however, that the invention has other applications including controlling electric vehicles, heavy equipment such as off-road and construction vehicles, controlling machinery such as lathes, punches, compressors, and other machinery to which it is desirable to limit access, or the like.
Heretofore, numerous types of anti-theft systems have been utilized for motor vehicles. Some of these devices have included an ignition control device which is located under the hood for selectively permitting and blocking electrical power to reach the vehicle's ignition system. These systems further include a mechanism for selectively activating the ignition control device such that electrical power is permitted to pass to the ignition. Typically, this means includes a keyboard located on the dashboard into which the operator punches a preselected code. If the proper code is entered, the ignition control circuit is enabled to pass electrical power to the ignition.
One of the problems with the prior art systems is that to connect lead wires between the keyboard and the ignition control circuit, it was necessary to cut a hole through the firewall of the vehicle. The lead wires were threaded through the hole in the firewall to the ignition control circuit. Cutting and threading wires through the firewall is difficult and time consuming. This cutting and threading wires through the firewall is particularly difficult for the do-it-yourself installer who purchases the anti-theft system in a kit.
One solution was to connect a radio transmitter with a keyboard and a radio receiver with the ignition control device. However, radio control systems have inherent drawbacks. In a radio control system, it is possible to receive signals which could inadvertently disarm the system or actuate the alarm from like anti-theft systems in nearby vehicles, garage door openers, electrical storms, stray harmonics of broadcast radio, and the like. Another draw back to the radio controlled systems is maintaining fresh batteries within the transmitter module. Further, FCC licensing may be required of the owner of radio controlled systems.